1. Field of the Invention
The present invention relates to otic wire spring prosthesis in general and in particular to a middle ear prosthesis used in ossicular reconstruction
2. Description of the Prior Art
It is presently known to repair the sound conducting mechanism of the middle ear by surgical implantation of various types of prosthesis. Such repair may involve either total reconstruction where all three ossicles between the tympanic membrance and the oval window of the inner ear are replaced by a prosthesis, partial reconstruction wherein only the malleus and the incus or only the incus is replaced.
Known prior art prosthesis for reconstruction procedures have been made from various natural materials such as cartilage and bone, and from various man-made materials such as stainless steel and plastics like Teflon, Polyethelene, and Bio-compatible materials like Proplast and Plastipore New ceramics are also being developed such as Ceravital and Hydroxapatite.
Irrespective of the material most of the prosthetic devices known are usually one piece straight shaft devices having a head portion resting against the tympanic membrane with the opposite end pressing against the footplate of the stapes for complete reconstruction procedures or the stapes capitulum-superstructure for partial reconstruction procedures.
For a discussion of prior art prosthetic devices and the implanting techniques of same, the reader is referred to the following articles which discuss such devices in greater detail. These articles are (1) "BIOCOMPATIBLE OSSICULAR IMPLANTS" by John J. Shea, M.D. and John R. Emmett, M.D. appearing in Volume 104, April 1978, Issue of Arch. Otolaryngol; (2) "A DECADE OF TYMPANOPLASTY: PROGRESS OR REGRESS?" by David F. Austin, M.D. appearing in the May 1982 Issue of Larynogoscope 92; (3) "OSSICULAR CHAIN RECONSTRUCTION: THE TORP AND PORP AND CHRONIC EAR DISEASE" by C. Gary Jackson, M.D. et al appearing in the Aug. 1983 Issue of Larynogoscope; (4) BIOACTINE GLASS - CERAMIC IN EAR SURGERY: AUINIAL STUDIES AND CLINICAL RESULTS by Reck, R. appearing in February, 1984 Issue of Larynogoscope (Suppl. 33); and (5) RECONSTRUCTION OF THE OSSICULAR CHAIN WITH HYDROXAPATITE INPLANTS by J. Grote appearing in Annals of Otology Rhinology and Laryngology (Suppl. 123), Volume 95, March - April 1986.
Wire prosthetic devices are also known. Some such devices consist of a straight shaft stainless steel wire with a transverse bar located at one end of the wire shaft. The bar or any other transverse section is intended to limit the insertion of the device into any base material such as cartilage located under the tympanic membrane. All straight shaft prosthetic devices give rise to certain problems due to their lack of flexibility. Slight outward retraction and/or shift of the tympanic membrane which may occur during the post-operative healing process causes the tip of the prosthetic device to lift off or slip from either the footplate or stapes head, depending upon the type of reconstruction, resulting in a loss of the tension pressure between the tympanic membrane and the footplate initially set by the surgeon implanting the prosthetic device. As a result, the patient does not hear as well after healing from the operation as he did when the operation was just performed. When the ear is subjected to a loud noise, the extreme deflection of the tympanic membrane caused by the noise may damage the inner ear--the cochlea. Also, with a straight shaft prosthesis there is no protection for inner ear damage from external physical trauma to the ear.
Coil spring wire prosthesis such as may be found in U.S. Pat. No. 4,624,672 issued to the present Applicant Edmundas Lenkauskas M.D., provides flexibility to absorb shocks induced by loud noises or other external trauma to the ear. They also have sufficient flexibility to compensate for any displacement change between the tympanic membrane and the inner ear due to outward retraction occurring during the post operative healing process to maintain sufficient pressure between them to insure adequate hearing restoration over an extended period of time. However, such prosthesis have relatively large central coil to provide such flexibility. This requires an accurate installation technique into the middle ear space to prevent the touching of the coil to the walls of the middle ear or promontory which may cause a short circuiting of the sound energy. Also such prostheses did not have the ability in the prosthesis head to adjust to positional variances of the tympanicmembrane. Thus equal distribution of pressure to the undersuface of the tympanic membrane was not provided.